xdelta: initial handler for invalid xdelta target window checksums

gogdl/dl/managers/task_executor.py

@@ -681,7 +681,10 @@ def process_writer_task_results(self, shm_cond: Condition):
 
                 if not res.success:
                     self.logger.fatal("Task writer failed")
-
+                    if res.task.flags & generic.TaskFlag.PATCH:
+                        # Handle full redownload?
+                        pass
+
                 self.progress.update_bytes_written(res.written)
                 if res.task.old_file:
                     self.progress.update_bytes_read(res.task.size or 0)

gogdl/dl/objects/v2.py

@@ -239,8 +239,10 @@ def __init__(self):
     def get(cls,  manifest, old_manifest, lang: str, dlcs: list, api_handler):
         if isinstance(manifest, v1.Manifest) or isinstance(old_manifest, v1.Manifest):
             return None
-        from_build = old_manifest.data['buildId']
-        to_build = manifest.data['buildId']
+        from_build = old_manifest.data.get('buildId')
+        to_build = manifest.data.get('buildId')
+        if not from_build or not to_build:
+            return None
         dlc_ids = [dlc["id"] for dlc in dlcs]
         patch_meta = dl_utils.get_zlib_encoded(api_handler, f'{constants.GOG_CONTENT_SYSTEM}/products/{manifest.product_id}/patches?_version=4&from_build_id={from_build}&to_build_id={to_build}')[0]
         if not patch_meta or patch_meta.get('error'):

gogdl/xdelta/objects.py

@@ -1,5 +1,6 @@
 from dataclasses import dataclass
 from io import IOBase, BytesIO
+from typing import Optional
 
 @dataclass
 class CodeTable:
@@ -69,6 +70,8 @@ class Context:
     cpy_len: int = 0
     cpy_off: int = 0
     dec_winoff: int = 0
+
+    target_buffer: Optional[bytearray] = None
 
 def build_code_table():
     table: list[Instruction] = []
@@ -132,3 +135,5 @@ def build_code_table():
 
 CODE_TABLE = build_code_table()
 
+class ChecksumMissmatch(AssertionError):
+    pass

gogdl/xdelta/patcher.py

@@ -1,4 +1,5 @@
 from io import BytesIO
+from zlib import adler32
 from gogdl.xdelta import objects
 
 # Convert stfio integer
@@ -126,16 +127,19 @@ def patch(source: str, patch: str, out: str):
         delta_encoding_length = read_integer_stream(patch_handle)
 
         window_length = read_integer_stream(patch_handle)
+        context.target_buffer = bytearray()
 
         delta_indicator = patch_handle.read(1)[0]
 
         add_run_data_length = read_integer_stream(patch_handle)
         instructions_length = read_integer_stream(patch_handle)
         addresses_length = read_integer_stream(patch_handle)
 
+        parsed_sum = 0
         if adler32_sum:
             checksum = patch_handle.read(4)
-
+            parsed_sum = int.from_bytes(checksum, 'big')
+
 
         context.data_sec = BytesIO(patch_handle.read(add_run_data_length))
         context.inst_sec = BytesIO(patch_handle.read(instructions_length))
@@ -164,6 +168,13 @@ def patch(source: str, patch: str, out: str):
             while current2.type != objects.XD3_NOOP:
                 decode_halfinst(context, current2)
 
+        if adler32_sum:
+            calculated_sum = adler32(context.target_buffer)
+            if parsed_sum != calculated_sum:
+                raise objects.ChecksumMissmatch
+
+        context.target.write(context.target_buffer)
+
         indicator = patch_handle.read(1)
         if not len(indicator):
             win_indicator = None
@@ -172,6 +183,7 @@ def patch(source: str, patch: str, out: str):
         win_number += 1
 
 
+    dst_handle.flush()
     src_handle.close()
     patch_handle.close()
     dst_handle.close()